The Slide Projector (Physics of Technology Series)
Publication date 1975
Topics physics education, science education, technology education, optics, light physics, engineering education
A module on geometrical and physical optics.
Covers geometrical optics of thin lenses (with principal ray diagrams), magnification, reflection, refraction, and compound lenses. The module, which can be completed in two weeks, is appropriate for use as an "entry" module, and no special equipment is necessary. Either THE SLIDE PROJECTOR or THE CAMERA provides reasonably complete coverage of geometrical optics.
Part of the Physics of Technology program, a 27-module introduction to physics at a pre-calculus level. The American Institute of Physics coordinated this program in the 1970s, with modules created by Florissant Valley Community College, Oak Ridge Associated Universities, the State University of New York at Binghamton, and TERC.
From the Instructor’s Manual:
This module has three main aims. First, the module conveys essential aspects of geometrical optics in the familiar context of an ordinary slide projector. Material covered includes such items as the use of ray diagrams to locate images, differences between real and virtual images, the "Universal Lens Rule" relating object and image positions, and so on.
Second, the module shows the broad applicability of optics by discussing a variety of other devices, in addition to the slide projector, which can be understood on a similar basis. In particular, it is shown that many devices are in essence "projectors" even though they go by different names and perform different functions. These devices include the camera, the microscope, the telescope, and even the human eye.
Third, the module suggests the fundamental basis of optics and some of its limitations by including a limited discussion of wave theory. For instance, the theoretical meaning of "rays" in terms of the motion of wave fronts is introduced, and this meaning is related to the formation and manipulation of practical rays in the laboratory. The basic "diffraction limit" which determines the minimum spreading of practical rays is mentioned and the student can see this operating by a simple experiment with the slide projector.
Unlike most of the modules in the Physics of Technology series, the Slide Projector is divided into only two sections. This means that the work is meant to be completed in two weeks instead of the usual three. There are two reasons for this difference. First, many instructors will not wish to devote more than two weeks to what is sometimes regarded as a minor, albeit important and interesting, aspect of introductory physics. Second, the shorter form of the module means that instructors who do wish to pursue optics further can do so along two alternative paths.
One path is to examine more deeply the technical aspects of geometrical optics itself, such as applications to "thick" lenses and complicated lens systems. This can be accomplished by following the Projector with, for example, the Binoculars module. A second possible route is to follow the Projector with a module such as the Spectrophotometer . which uses optics as a tool to study the spectral properties of light. This in turn leads to numerous applications in the area of materials science. As is well known, spectrophotometers find wide use in medicine, industry, etc., so that their study affords an especially effective approach to elements of applied modern physics.
One additional feature of the Projector module deserves mention. This concerns the lack of any special equipment required for its use, other than the projector itself. In most cases, instructors will already have access to a projector which can be employed without modification, such as the standard "Carousel" projector depicted in the text. The experiments will not in any way damage the projector, since the only manipulations involved are the usual ones of focusing, removing the lens barrel, examining the bulb, etc. Besides the projector, only minor items are needed, which are either readily available as such or can be easily fabricated by the instructor or students from available materials (black masking tape, razor blades, 2" x 2" microscope slides, etc.). Thus, the experiments in the module can be implemented with minimal trouble and expense. Furthermore, this will avoid some of the contrived appearance of standard introductory optics apparatus.
There are no special prerequisites for this module, except that for the Physics of Technology series as a whole: high school algebra.
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